The Russian internet watchdog has demanded an explanation from Facebook and Instagram over the blocking of social media accounts belonging to the controversial Chechen leader, Ramzan Kadyrov.

Kadyrov has accused the US government of pressuring the social networks to disable his accounts, which he said were blocked on Saturday without explanation. The US imposed travel and financial sanctions on Kadyrov last week over numerous allegations of human rights abuses.

The former rebel fighter, who is now loyal to the Russian president, Vladimir Putin, is a fan of social media, particularly Instagram, which he has used in recent years to make barely veiled death threats against Kremlin critics.

Kadyrov has more than 3 million followers on his Russian-language Instagram account and more than 750,000 on Facebook. His less popular English-language Instagram account is still active.

Roskomnadzor, the media and telecoms regulator, said it would officially request an answer from the companies.

Leonid Levin, the head of the Russian parliament’s information technologies and communications committee, suggested the move by Facebook and Instagram was an attack on freedom of speech.

Dzhambulat Umarov, the Chechen press and information minister, described the blocking of Kadyrov’s accounts as a “vile” cyber-attack by the US.

Neither Instagram nor Facebook had commented at the time of publication.

In 2015, Kadyrov urged Chechen men not to let their wives use the WhatsApp messaging service after an online outcry over the forced marriage of a 17-year-old Chechen to a 47-year-old police chief. “Do not write such things. Men, take your women out of WhatsApp,” he said.